/*
 *  ME218_I2C.c
 *  ArduinoOnXcode
 *
 *  Created by Rick Miley on 3/17/11.
 *  Copyright 2011 __MyCompanyName__. All rights reserved.
 *
 */

#include <ME218_I2C.h>


/*
 twi.c - TWI/I2C library for Wiring & Arduino
 Copyright (c) 2006 Nicholas Zambetti.  All right reserved.
 
 This library is free software; you can redistribute it and/or
 modify it under the terms of the GNU Lesser General Public
 License as published by the Free Software Foundation; either
 version 2.1 of the License, or (at your option) any later version.
 
 This library is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 Lesser General Public License for more details.
 
 You should have received a copy of the GNU Lesser General Public
 License along with this library; if not, write to the Free Software
 Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */





#ifndef cbi
#define cbi(sfr, bit) (_SFR_BYTE(sfr) &= ~_BV(bit))
#endif

#ifndef sbi
#define sbi(sfr, bit) (_SFR_BYTE(sfr) |= _BV(bit))
#endif



// ================================== twi_init ===============================
/* 
 * Function twi_init
 * Desc     readys twi pins and sets twi bitrate
 * Input    none
 * Output   none
 */
void twi_init(void)
{
	// initialize state
	twi_state = TWI_READY;
	
#if defined(__AVR_ATmega168__) || defined(__AVR_ATmega8__) || defined(__AVR_ATmega328P__)
    // activate internal pull-ups for twi
    // as per note from atmega8 manual pg167
    sbi(PORTC, 4);
    sbi(PORTC, 5);
#else
    // activate internal pull-ups for twi
    // as per note from atmega128 manual pg204
    sbi(PORTD, 0);
    sbi(PORTD, 1);
#endif
	
	// initialize twi prescaler and bit rate
	cbi(TWSR, TWPS0);
	cbi(TWSR, TWPS1);
	TWBR = ((CPU_FREQ / TWI_FREQ) - 16) / 2;
	
	/* twi bit rate formula from atmega128 manual pg 204
	 SCL Frequency = CPU Clock Frequency / (16 + (2 * TWBR))
	 note: TWBR should be 10 or higher for master mode
	 It is 72 for a 16mhz Wiring board with 100kHz TWI */
	
	// enable twi module, acks, and twi interrupt
	TWCR = _BV(TWEN) | _BV(TWIE) | _BV(TWEA);
}

/* 
 * Function twi_slaveInit
 * Desc     sets slave address and enables interrupt
 * Input    none
 * Output   none
 */
void twi_setAddress(uint8_t address)
{
	// set twi slave address (skip over TWGCE bit)
	TWAR = address << 1;
}

/* 
 * Function twi_readFrom
 * Desc     attempts to become twi bus master and read a
 *          series of bytes from a device on the bus
 * Input    address: 7bit i2c device address
 *          data: pointer to byte array
 *          length: number of bytes to read into array
 * Output   number of bytes read
 */
uint8_t twi_readFrom(uint8_t address, uint8_t* data, uint8_t length)
{
	uint8_t i;
	
	// ensure data will fit into buffer
	if(TWI_BUFFER_LENGTH < length){
		return 0;
	}
	
	// wait until twi is ready, become master receiver
	while(TWI_READY != twi_state){
		continue;
	}
	twi_state = TWI_MRX;
	// reset error state (0xFF.. no error occured)
	twi_error = 0xFF;
	
	// initialize buffer iteration vars
	twi_masterBufferIndex = 0;
	twi_masterBufferLength = length-1;  // This is not intuitive, read on...
	// On receive, the previously configured ACK/NACK setting is transmitted in
	// response to the received byte before the interrupt is signalled. 
	// Therefor we must actually set NACK when the _next_ to last byte is
	// received, causing that NACK to be sent in response to receiving the last
	// expected byte of data.
	
	// build sla+w, slave device address + w bit
	twi_slarw = TW_READ;
	twi_slarw |= address << 1;
	
	// send start condition
	TWCR = _BV(TWEN) | _BV(TWIE) | _BV(TWEA) | _BV(TWINT) | _BV(TWSTA);
	
	// wait for read operation to complete
	while(TWI_MRX == twi_state){
		continue;
	}
	
	if (twi_masterBufferIndex < length)
		length = twi_masterBufferIndex;
	
	// copy twi buffer to data
	for(i = 0; i < length; ++i){
		data[i] = twi_masterBuffer[i];
	}
	
	return length;
}

/* 
 * Function twi_writeTo
 * Desc     attempts to become twi bus master and write a
 *          series of bytes to a device on the bus
 * Input    address: 7bit i2c device address
 *          data: pointer to byte array
 *          length: number of bytes in array
 *          wait: boolean indicating to wait for write or not
 * Output   0 .. success
 *          1 .. length to long for buffer
 *          2 .. address send, NACK received
 *          3 .. data send, NACK received
 *          4 .. other twi error (lost bus arbitration, bus error, ..)
 */
uint8_t twi_writeTo(uint8_t address, uint8_t* data, uint8_t length, uint8_t wait)
{
	uint8_t i;
	
	// ensure data will fit into buffer
	if(TWI_BUFFER_LENGTH < length){
		return 1;
	}
	
	// wait until twi is ready, become master transmitter
	while(TWI_READY != twi_state){
		continue;
	}
	twi_state = TWI_MTX;
	// reset error state (0xFF.. no error occured)
	twi_error = 0xFF;
	
	// initialize buffer iteration vars
	twi_masterBufferIndex = 0;
	twi_masterBufferLength = length;
	
	// copy data to twi buffer
	for(i = 0; i < length; ++i){
		twi_masterBuffer[i] = data[i];
	}
	
	// build sla+w, slave device address + w bit
	twi_slarw = TW_WRITE;
	twi_slarw |= address << 1;
	
	// send start condition
	TWCR = _BV(TWEN) | _BV(TWIE) | _BV(TWEA) | _BV(TWINT) | _BV(TWSTA);
	
	// wait for write operation to complete
	while(wait && (TWI_MTX == twi_state)){
		continue;
	}
	
	if (twi_error == 0xFF)
		return 0;	// success
	else if (twi_error == TW_MT_SLA_NACK)
		return 2;	// error: address send, nack received
	else if (twi_error == TW_MT_DATA_NACK)
		return 3;	// error: data send, nack received
	else
		return 4;	// other twi error
}

/* 
 * Function twi_transmit
 * Desc     fills slave tx buffer with data
 *          must be called in slave tx event callback
 * Input    data: pointer to byte array
 *          length: number of bytes in array
 * Output   1 length too long for buffer
 *          2 not slave transmitter
 *          0 ok
 */
uint8_t twi_transmit(uint8_t* data, uint8_t length)
{
	uint8_t i;
	
	// ensure data will fit into buffer
	if(TWI_BUFFER_LENGTH < length){
		return 1;
	}
	
	// ensure we are currently a slave transmitter
	if(TWI_STX != twi_state){
		return 2;
	}
	
	// set length and copy data into tx buffer
	twi_txBufferLength = length;
	for(i = 0; i < length; ++i){
		twi_txBuffer[i] = data[i];
	}
	
	return 0;
}

/* 
 * Function twi_attachSlaveRxEvent
 * Desc     sets function called before a slave read operation
 * Input    function: callback function to use
 * Output   none
 */
void twi_attachSlaveRxEvent( void (*function)(uint8_t*, int) )
{
	twi_onSlaveReceive = function;
}

/* 
 * Function twi_attachSlaveTxEvent
 * Desc     sets function called before a slave write operation
 * Input    function: callback function to use
 * Output   none
 */
void twi_attachSlaveTxEvent( void (*function)(void) )
{
	twi_onSlaveTransmit = function;
}

/* 
 * Function twi_reply
 * Desc     sends byte or readys receive line
 * Input    ack: byte indicating to ack or to nack
 * Output   none
 */
void twi_reply(uint8_t ack)
{
	// transmit master read ready signal, with or without ack
	if(ack){
		TWCR = _BV(TWEN) | _BV(TWIE) | _BV(TWINT) | _BV(TWEA);
	}else{
		TWCR = _BV(TWEN) | _BV(TWIE) | _BV(TWINT);
	}
}

/* 
 * Function twi_stop
 * Desc     relinquishes bus master status
 * Input    none
 * Output   none
 */
void twi_stop(void)
{
	// send stop condition
	TWCR = _BV(TWEN) | _BV(TWIE) | _BV(TWEA) | _BV(TWINT) | _BV(TWSTO);
	
	// wait for stop condition to be exectued on bus
	// TWINT is not set after a stop condition!
	while(TWCR & _BV(TWSTO)){
		continue;
	}
	
	// update twi state
	twi_state = TWI_READY;
}

/* 
 * Function twi_releaseBus
 * Desc     releases bus control
 * Input    none
 * Output   none
 */
void twi_releaseBus(void)
{
	// release bus
	TWCR = _BV(TWEN) | _BV(TWIE) | _BV(TWEA) | _BV(TWINT);
	
	// update twi state
	twi_state = TWI_READY;
}

// Vector 24

SIGNAL(TWI_vect)
{
	switch(TW_STATUS){
			// All Master
		case TW_START:     // sent start condition
		case TW_REP_START: // sent repeated start condition
			// copy device address and r/w bit to output register and ack
			TWDR = twi_slarw;
			twi_reply(1);
			break;
			
			// Master Transmitter
		case TW_MT_SLA_ACK:  // slave receiver acked address
		case TW_MT_DATA_ACK: // slave receiver acked data
			// if there is data to send, send it, otherwise stop 
			if(twi_masterBufferIndex < twi_masterBufferLength){
				// copy data to output register and ack
				TWDR = twi_masterBuffer[twi_masterBufferIndex++];
				twi_reply(1);
			}else{
				twi_stop();
			}
			break;
		case TW_MT_SLA_NACK:  // address sent, nack received
			twi_error = TW_MT_SLA_NACK;
			twi_stop();
			break;
		case TW_MT_DATA_NACK: // data sent, nack received
			twi_error = TW_MT_DATA_NACK;
			twi_stop();
			break;
		case TW_MT_ARB_LOST: // lost bus arbitration
			twi_error = TW_MT_ARB_LOST;
			twi_releaseBus();
			break;
			
			// Master Receiver
		case TW_MR_DATA_ACK: // data received, ack sent
			// put byte into buffer
			twi_masterBuffer[twi_masterBufferIndex++] = TWDR;
		case TW_MR_SLA_ACK:  // address sent, ack received
			// ack if more bytes are expected, otherwise nack
			if(twi_masterBufferIndex < twi_masterBufferLength){
				twi_reply(1);
			}else{
				twi_reply(0);
			}
			break;
		case TW_MR_DATA_NACK: // data received, nack sent
			// put final byte into buffer
			twi_masterBuffer[twi_masterBufferIndex++] = TWDR;
		case TW_MR_SLA_NACK: // address sent, nack received
			twi_stop();
			break;
			// TW_MR_ARB_LOST handled by TW_MT_ARB_LOST case
			
			// Slave Receiver
		case TW_SR_SLA_ACK:   // addressed, returned ack
		case TW_SR_GCALL_ACK: // addressed generally, returned ack
		case TW_SR_ARB_LOST_SLA_ACK:   // lost arbitration, returned ack
		case TW_SR_ARB_LOST_GCALL_ACK: // lost arbitration, returned ack
			// enter slave receiver mode
			twi_state = TWI_SRX;
			// indicate that rx buffer can be overwritten and ack
			twi_rxBufferIndex = 0;
			twi_reply(1);
			break;
		case TW_SR_DATA_ACK:       // data received, returned ack
		case TW_SR_GCALL_DATA_ACK: // data received generally, returned ack
			// if there is still room in the rx buffer
			if(twi_rxBufferIndex < TWI_BUFFER_LENGTH){
				// put byte in buffer and ack
				twi_rxBuffer[twi_rxBufferIndex++] = TWDR;
				twi_reply(1);
			}else{
				// otherwise nack
				twi_reply(0);
			}
			break;
		case TW_SR_STOP: // stop or repeated start condition received
			// put a null char after data if there's room
			if(twi_rxBufferIndex < TWI_BUFFER_LENGTH){
				twi_rxBuffer[twi_rxBufferIndex] = '\0';
			}
			// sends ack and stops interface for clock stretching
			twi_stop();
			// callback to user defined callback
			twi_onSlaveReceive(twi_rxBuffer, twi_rxBufferIndex);
			// since we submit rx buffer to "wire" library, we can reset it
			twi_rxBufferIndex = 0;
			// ack future responses and leave slave receiver state
			twi_releaseBus();
			break;
		case TW_SR_DATA_NACK:       // data received, returned nack
		case TW_SR_GCALL_DATA_NACK: // data received generally, returned nack
			// nack back at master
			twi_reply(0);
			break;
			
			// Slave Transmitter
		case TW_ST_SLA_ACK:          // addressed, returned ack
		case TW_ST_ARB_LOST_SLA_ACK: // arbitration lost, returned ack
			// enter slave transmitter mode
			twi_state = TWI_STX;
			// ready the tx buffer index for iteration
			twi_txBufferIndex = 0;
			// set tx buffer length to be zero, to verify if user changes it
			twi_txBufferLength = 0;
			// request for txBuffer to be filled and length to be set
			// note: user must call twi_transmit(bytes, length) to do this
			twi_onSlaveTransmit();
			// if they didn't change buffer & length, initialize it
			if(0 == twi_txBufferLength){
				twi_txBufferLength = 1;
				twi_txBuffer[0] = 0x00;
			}
			// transmit first byte from buffer, fall
		case TW_ST_DATA_ACK: // byte sent, ack returned
			// copy data to output register
			TWDR = twi_txBuffer[twi_txBufferIndex++];
			// if there is more to send, ack, otherwise nack
			if(twi_txBufferIndex < twi_txBufferLength){
				twi_reply(1);
			}else{
				twi_reply(0);
			}
			break;
		case TW_ST_DATA_NACK: // received nack, we are done 
		case TW_ST_LAST_DATA: // received ack, but we are done already!
			// ack future responses
			twi_reply(1);
			// leave slave receiver state
			twi_state = TWI_READY;
			break;
			
			// All
		case TW_NO_INFO:   // no state information
			break;
		case TW_BUS_ERROR: // bus error, illegal stop/start
			twi_error = TW_BUS_ERROR;
			twi_stop();
			break;
	}
}






